Chemical and biological sensing systems are important in a number of different applications, such as medical, environmental, agricultural, military and industrial applications, to name a few. ChemFET sensing systems based on chemically sensitive field effect transistors have in particular been investigated for decades and have demonstrated some commercial applicability, although mainly for pH and pH-mediated enzyme sensors (EnFETs) because of the immense technical difficulties involved in the species-specific, highly sensitive biochemical sensing that is needed for biotech and medical usage.
One type of ChemFET sensing system employs a nanowire sensing element that is functionalized (with a functional agent) to enable the nanowire to electrically respond to the presence of an analyte in a sample. Interaction between the functionalized nanowire and the analyte may cause, for example, the generation of an electric field that, in turn, causes a detectable change in an electrical property of the nanowire (e.g., a detectable shift in electrical conductance). This type of ChemFET sensing system may alternatively be referred to herein as a “nanowire based” sensing system. Examples of a “nanowire based” sensing system are described in the patent literature. See, for example, PCT Application WO 02/48701, having international filing date of Dec. 11, 2001, entitled “NANOSENSORS”, by inventors Lieber et.al.
Nanowire based sensing systems offer a number of advantages including very high sensitivity and the ability to monitor very small sample sizes. There is a need, however, to improve upon the manufacturability of these sensing systems and to expand their capabilities.